How to remain detached (when insert a WordPress image into a post)

how-to-remain-detached.php

<?php

/**
 * Implement 'wp_ajax_send-attachment-to-editor' to not attach an unattached media item.
 * 
 * In WordPress TRAC 22085 there was a change.
 * that caused unattached media files (images) to be attached to posts if they are inserted into the post.
 *
 * If you don't like this strategy you can disable it using this simple, rather hacky, action hook.
 *
 * Trac Ticket: https://core.trac.wordpress.org/ticket/32999
 * See: http://herbmiller.me/2015/07/15/h2gd-part-45-how-to-remain-detached/
 */
function dont_attach( $blah ) {
        $_POST['post_id'] = 0;
}
/*
 * Hook into the AJAX request before WordPress, using priority 0
 */ 
add_action( 'wp_ajax_send-attachment-to-editor', 'dont_attach', 0 );

?>